elia / bert /activations.py
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import logging
import math
import torch
import torch.nn.functional as F
logger = logging.getLogger(__name__)
def swish(x):
return x * torch.sigmoid(x)
def _gelu_python(x):
""" Original Implementation of the gelu activation function in Google Bert repo when initially created.
For information: OpenAI GPT's gelu is slightly different (and gives slightly different results):
0.5 * x * (1 + torch.tanh(math.sqrt(2 / math.pi) * (x + 0.044715 * torch.pow(x, 3))))
This is now written in C in torch.nn.functional
Also see https://arxiv.org/abs/1606.08415
"""
return x * 0.5 * (1.0 + torch.erf(x / math.sqrt(2.0)))
def gelu_new(x):
""" Implementation of the gelu activation function currently in Google Bert repo (identical to OpenAI GPT).
Also see https://arxiv.org/abs/1606.08415
"""
return 0.5 * x * (1.0 + torch.tanh(math.sqrt(2.0 / math.pi) * (x + 0.044715 * torch.pow(x, 3.0))))
if torch.__version__ < "1.4.0":
gelu = _gelu_python
else:
gelu = F.gelu
def gelu_fast(x):
return 0.5 * x * (1.0 + torch.tanh(x * 0.7978845608 * (1.0 + 0.044715 * x * x)))
ACT2FN = {
"relu": F.relu,
"swish": swish,
"gelu": gelu,
"tanh": torch.tanh,
"gelu_new": gelu_new,
"gelu_fast": gelu_fast,
}
def get_activation(activation_string):
if activation_string in ACT2FN:
return ACT2FN[activation_string]
else:
raise KeyError("function {} not found in ACT2FN mapping {}".format(activation_string, list(ACT2FN.keys())))